The present invention relates to controls for a hydraulically driven vehicle such as a hydraulic pressure type power shovel or the like, wherein the direction of travel is subjected to control by a pair of hydraulic motors arranged in place on the right and left sides, thereof respectively.
In conventional practice, controls of this category have usually comprised a pair of independent control levers arranged in place on the right and left sides and connected with a pair of control sections of a hydraulic motor for driving the right and left drive wheels, respectively.
However, in the case of conventional technology of this category, operational control is complicated due mainly to the dual system of control levers; and therefore, special skill has been required for proper operation of such a vehicle.
One object of the present invention rests in providing controls for a hydraulically driven vehicle which are completely capable of eliminating said operational defects inherent in conventional technology.
Another object of the present invention rests in providing controls for a hydraulically driven vehicle which are completely capable of causing the vehicle to engage in forward movement, rearward movement, right revolution, and left revolution as well. All of this is achieved by the proper actuation of a lever for forward and rearward travel and a pair of pedals for additional directional control arranged in place on the right and on the left sides, respectively.
Another object of the present invention rests in providing controls for a hydraulically driven vehicle, wherein a lever for forward and rearward travel and a pair of pedals for additional directional control arranged in place on the right and left sides, respectively are kept free from being mechanically engaged with each other in mechanical terms and comprise independent operating mechanisms, respectively.
Still other objects of the present invention rest with providing controls for a hydraulically driven vehicle, which are specifically designed so as to be capable of conducting proper damping for parking in a secure manner, and wherein the hydraulic pressure source for driving the motor for travel and the hydraulic pressure source for the parking brake are so designed as to be one and the same.
In the present invention, a vehicle can be caused to engage in forward movement and rearward movement by the proper operation of a lever for the control of travel in a manner effectuating a change-over to that end.
When either one of said pair of pedals arranged on the right side and the left side for the purpose of conducting additional directional control is put into operation, while the vehicle is in a state of forward movement or rearward movement, the pilot-actuated change-over valve for additional directional control arranged on the side of the respective pedals is actuated to a position for drainage, and the valve for travel arranged on the side of the pedals thus actuated is set in the neutral position.
Therefore, in the situation where both the lever for forward or rearward direction control of travel and the pedals for additional directional control are actuated at the same time, the vehicle is thereby put into a right revolution and left revolution also.
Since the lever for forward or rearward directional control of travel and the pedals for additional directional control are kept from being engaged with each other in mechanical terms, the operating mechanism for the lever for forward or rearward travel and that for the pedals for right or left directional control can be simplified respectively, in terms of the constitution thereof; therefore, even in a case where the lever for forward or rearward travel is subjected to change-over for operation thereof in a state wherein the pedals for additional directional control are actuated, the force required thereof can be properly kept from increasing.
The same hydraulic pressure source can now be employed for dual purposes. First, as the one for the pilot for driving the motors for travel arranged on the right side and on the left side for forward revolution and reverse revolution on the one hand and, secondly, as the one for the brake for the operation of parking on the other hand. Because of this, the hydraulic pressure circuit can be so designed as to be simplified, and a hydraulic circuit for the parking brake can be omitted in an advantageous manner.
When the valve of the parking brake is set in a position for drainage, and the parking brake is thus put into a state for damping, the hydraulic pressure discharged out of the hydraulic pressure source for the pilot is properly checked from flowing into the forward-reverse drive control circuit of the motor for travel. In other words, the hydraulic pressure is prevented from flowing into the pilot-actuated traveling valves arranged on the right side and on the left side; thus, a vehicle can be properly checked from traveling.
Therefore, now that the vehicle can be properly checked from traveling, with the parking brake kept intact in the state of being thus damped, each and every one of the sections interrelated therewith can be prevented, in a proper manner, from being subjected to breakage.
Furthermore, even in a case when an engine has been started for operation, parking can be damped in a proper manner by setting the valve of the parking brake at the position for drainage.
Also, in the case where the lever for travel is actuated immediately after starting the engine, the hydraulic pressure discharged out of the hydraulic pressure source for the pilot is caused to fill the space in the primary chamber of the parking brake. Then, the pilot-actuated traveling valve is properly changed over for actuation only after the parking brake is in a state for non-damping and the vehicle is caused to travel in a state wherein the parking brake is thus kept damped in a proper manner, and respective sections can be properly prevented from being subjected to breakage.
In other words, in the present invention, the working hydraulic pressure in the primary chamber of the parking brake and the working pressure of the pilot-actuated traveling valve are so designed as to be one and the same.